systems in good operating condition. This includes
a. This technical manual provides basic infor-
keeping equipment information files and necessary
mation for facilities personnel regarding the oper-
records of the maintenance work performed.
ation and maintenance of small heating systems and
related equipment. Generally, the manual covers
1-5. Systems overview.
low pressure steam boilers (less than 15 psig), low
The main heat conveying media for space heating
pressure hot water boilers (less than 30 psig), space
systems are steam, hot water, and warm air.
heaters, unit heaters, and warm air furnaces. The
a. Steam. Water heated to the boiling point
term “small” is used in the context of this manual to
evaporates and produces steam as long as heat is
differentiate from the high pressure systems and
added. If the heat is removed or reduced, evapora-
equipment that are covered in detail in TM 5-650,
tion will stop or decrease. The quantity of heat
Central Boiler Plants.
contained in each pound of steam depends on its
b. This manual makes reference to specific types
pressure and temperature. Steam can be generated
of equipment commonly in use at Army installa-
and used as either saturated or superheated steam.
tions. System and equipment descriptions contained
Chapter 4 gives detailed information on steam
in the manual are general in nature. Equipment
systems.
manufacturers* technical literature and manuals
(1) Saturated steam. For each steam pressure,
should also be used for reference, training, and
there is a specific temperature at which the steam
troubleshooting specific equipment.
will become saturated. When steam is saturated, a
drop in temperature or an increase in pressure will
1-2. References.
cause part of the steam to revert to water. There
Related publications are listed in Appendix A.
are two types of saturated steam: dry, i.e., without
moisture; and wet, which is intermingled with
1-3. Abbreviations and terms.
moisture, mist or spray. Saturated steam is
Abbreviations and special terms used in this manual
commonly used for space heating and process heat.
are explained in the Glossary.
(2) Superheated steam. When steam has a
temperature higher than its corresponding satura-
1-4. Organization and responsibility.
tion pressure, it is called superheated steam. The
The operating and maintenance personnel for
difference between the temperature of superheated
heating systems are organized in accordance with
steam and its saturation temperature is called the
the applicable Army regulations and staffing guides.
superheat. Usually, superheated steam is generated
Supply and administrative support are provided by
in central heating plants when necessary to avoid
other divisions, branches, and/or sections within the
condensation in the steam lines of the plant and the
Directorate of Engineering and Housing. There are
distribution system, or to drive steam turbines.
significant differences at the installations in the
Normally in such instances, not more than 50F
quantity, type, and use of equipment. Therefore,
superheat is imparted to the steam.
personnel responsibilities may vary locally to
(3) Total heat content. A certain amount of
provide the necessary operating and maintenance
heat is needed to change water into steam. The
functions. In some cases, an individual may well
specific amount depends on the initial condition of
perform both operation and maintenance. In all
the water and the desired pressure and temperature
instances, coordination is required with the work
of the steam. The amount of heat required to
management functions (planning, estimating,
convert water at 32F into steam at a specific pres-
scheduling, recording data, etc.).
sure and temperature is called the total heat content
a. Operating personnel. Operating personnel
(or enthalpy) of the steam at that particular
have the responsibility to fire the equipment in the
pressure and temperature. As pressure rises from
most efficient and economical manner. This in-
atmospheric conditions up to about 450 psia, the
cludes the performance of equipment adjustments
total heat content of dry saturated steam increases.
and simple routine maintenance work consistent
At higher pressures, the total heat decreases as
with good operating practice.
b. Maintenance personnel. Maintenance person-
pressure increases. However, superheating
nel have the responsibility to maintain heating
increases the total heat content of the steam at any
1-1
TM 5-642
pressure. Any thermodynamic steam table will show
the areas where heating is required. Chapter 6 gives
the total heat content of steam at different pressures
detailed information on warm air systems.
and temperatures.
1-6. Energy conservation policy.
b. Hot water. Hot water is a very useful carrier
of heat. Circulating in a closed system, the water
a. All Army installations should have a manage-
absorbs heat in a boiler or heat exchanger and re-
ment improvement program that includes policies
leases it to the heat using equipment. Hot water
and guidelines relating to the efficient use and
systems can be classified as high temperature,
conservation of utilities. Conservation measures
medium temperature, and low temperature. Chap-
should be implemented by supervisory, operating
ter 5 gives detailed information on hot water sys-
and maintenance personnel and by the users. The
tems.
importance of keeping equipment properly used,
adjusted, and maintained cannot be overempha-
(1) High temperature water. High temperature
sized.
water (HTW), above 350F is usually generated in
b. Periodic reviews should be made of all factors
central heating plants and then delivered to the
influencing fuel selection to determine whether the
consumers by a distribution system. A heat ex-
fuel used still remains the most cost efficient for a
changer is normally used in each building to convert
particular installation. Also, the feasibility of
the HTW into low temperature water for use in
improving or modernizing firing methods for cur-
space heating.
rent fuels should be considered.
(2) Medium temperature water. Supply water
c. The greatest boiler operating efficiency is ob-
temperature for this type system ranges from 250F
tained when units are operated at or near their full
to 350F and is used for distribution systems, large
load ratings. Therefore, two boilers should never be
space heaters, absorption refrigeration, and indus-
operated if one can carry the load without
trial purposes.
exceeding its rating. Supervisors should review
(3) Low temperature water. Supply water tem-
daily operating logs to insure proper boiler oper-
perature for this type system is below 250F and is
ation. Give specific attention to the percentage of
used for space heating. Generally, this manual
CO in the flue gas and temperature of the gas.
2
covers low temperature hot water systems and
These are good indicators of operating efficiency
and depend on the proper balance between the rate
equipment.
of fuel feed, combustion air supply, draft, and stack
c. Warm air. Unlike steam and hot water, which
temperature.
are fed through pipes to space heating equipment
d. Periodically inspect heated facilities. Observe
from which heat is dispensed by radiation and
thermostat settings and advise users when incorrect
convection, warm air supplies direct heat. In warm
settings are found. Correct settings may be posted.
air systems, the cold air is heated by blowing it
Also, identify those facilities where excessive heat
through a furnace casing or heat exchanger. The
is lost due to improper insulation and open doors or
warmed air is then distributed through air ducts to
windows and take corrective actions.
1-2
TM 5-642